Design of natural and sustainable ingredients from sugarcane byproducts for cosmetic and skin care industry

Student thesis: Doctoral Thesis

Abstract

Sugarcane straw is a byproduct of sugar and ethanol production. This material is rich in phenolic compounds, known to have bioactive properties, including antimicrobial and antioxidant, which make them attractive for developing natural and sustainable ingredients for the cosmetic industry, namely preservative and anti-aging ingredients. However, the processing and use of sugarcane straw extracts for the cosmetic industry is yet unknown. Also, the bioactive properties of a sugarcane extract enriched with phenolic compounds need to be investigated in the event of being interesting for cosmetic industry. The safety of these ingredients on the skin and their impact on skin microbiota, which are fundamental to skin health, remains to be assessed. To assess the impact on the skin microbiota, less expensive and time-consuming techniques need to be developed. Thus, the main objectives of this thesis are 1) develop and optimize a process of extraction and purification of phenolic compounds from sugarcane straw; 2) develop a cosmetic ingredient based on the extract; 3) assess the preservative and anti-aging properties both in vitro and in vivo, as well as their capacity for dermal permeation.; 4) develop an in vitro preclinical model to test cosmetic ingredients on the skin microbiota; and 5) test the impact of the sugarcane straw extract-based ingredient on the skin microbiota. Initially an extraction and purification process to obtain the phenolic compounds from sugarcane straw was developed. After ethanolic extraction of the phenolic compounds, amberlite XAD-2 resin was used for purification of the extract. The purified extract was analyzed, resulting in the identification of 54 secondary metabolites, mainly hydroxybenzoic acids, hydroxycinnamic acids and flavones. The main compounds detected were chlorogenic acid, neochlorogenic acid and 3-O-feruloylquinic acid. Purification aimed to reduce the sugar content, and after, only a small number of monosaccharides, such as glucose, cellobiose and xylose + arabinose, were detected in the extracts. Additionally, the extracts displayed antioxidant activity, measured by ABTS and DPPH methods. Subsequently, the development of a cosmetic ingredient based on the phenolic compounds extract aimed to improve the solubility of the dry extract powder, and for that purpose, different cosmetic solvents (1,2-pentanediol, 1,2-hexanediol, dipropylene glycol and 1,5-pentanediol) were tested. The antimicrobial activity of the solubilized ingredients was evaluated against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. 1,2-Hexanediol afforded the ingredient with the best antimicrobial performance, with a minimum inhibitory concentration between 5 and 3 % (w/v), being the first compliant with USP 51 standards for cosmetic preservatives. The resulting ingredient formulation was chosen for further testing. Regarding the anti-aging properties of the engineered cosmetic ingredient, it was able to inhibit elastase (55 %), collagenase (25 %) and tyrosinase (47 %) and promote the hyaluronic acid production in fibroblasts (HDF) at non-cytotoxic and low-sensitization concentrations. Additionally, the ingredient reduced the levels of the pro-inflammatory cytokines IL-1α and IL-6 in immortalized keratinocytes (HaCaT) exposed to urban pollution particles. The ingredient's ability to permeate the skin was tested on a synthetic membrane that simulates the different layers of the skin, and around 67 % of the phenolic compounds present in the ingredient formulation remained on the surface of the skin, indicating that the ingredient has low dermal permeation. Sugarcane straw extract-based ingredient was incorporated in O/W and W/O emulsions and its stability was assessed in accelerated conditions following ISO/TR18811 directive. The anti-aging performance was evaluated in a cosmetic clinical trial, and the findings were verified by an external entity. This external evaluation not only covered the same parameters but also included assessments for anti-wrinkle effects, skin roughness, and elasticity. In summary, the ingredient did not enhance skin hydration, firmness, or exhibit significant anti-wrinkle or firming effects. Nevertheless, it was well-received and well-tolerated by the study participants. Finally, a preclinical in vitro skin microbiota model was developed, with test conditions optimized and validated using a reference ingredient with known in vivo data. The sugarcane straw extract-derived ingredient was then assessed using skin microbiota samples from 12 healthy volunteers, with microbial group impact analyzed through qPCR and next-generation sequencing (NGS). These results aligned with the manufacturer's in vivo findings, thus affirming the validity of the in vitro model. Sugarcane straw extract-based ingredient was found to have no effect on community α-diversity, although affected the relative abundance of Staphylococcus epidermidis. Thus, in this thesis, a purified extract from sugarcane straw rich in phenolic compounds was obtained and formulated to develop a cosmetic ingredient that has been shown to have preservative and anti-aging properties in vitro. Furthermore, a preclinical in vitro model was developed and validated as a tool for evaluating the impact of new cosmetic ingredients on the skin microbiota.
Date of Award15 Jan 2024
Original languageEnglish
Awarding Institution
  • Universidade Católica Portuguesa
SupervisorAna Raquel Madureira (Supervisor), Ana Lúcia Silva Oliveira (Co-Supervisor) & Sílvia Pedrosa (Co-Supervisor)

Keywords

  • Anti-aging
  • Cosmetic
  • Skin microbiota
  • Sugarcane
  • Sustainable

Designation

  • Doutoramento em Biotecnologia

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